The low-molecular-weight heparins (LMWHs) enoxaparin and dalteparin have shown superior
and equivalent efficacy, respectively, over unfractionated heparin (UFH) in patients
with unstable angina pectoris (UAP) or non-ST-segment elevation myocardial infarction
(NSTEMI). This study aimed to identify markers of blood cell activation that are independent
predictors of outcomes at 1 month and to compare the effects of enoxaparin, dalteparin,
and UFH on any such markers. In this multicenter, prospective, open-label study, 141
patients with UAP or NSTEMI were randomized to treatment for 48 to 120 hours with
enoxaparin (n = 46), dalteparin (n = 48), or UFH (n = 47). Blood samples were taken
at the time of randomization and after > or =48 hours of treatment but before catheterization.
Multivariate analysis identified increased plasma levels of von Willebrand factor
(vWF) and decreased platelet levels of glycoprotein Ib/IX complexes as independent
predictors of 1-month adverse outcome (a composite of death, myocardial infarction,
and recurrent ischemia). vWF release was strongly related to and may have been released
by inflammation as measured by C-reactive protein. Both LMWHs reduced the release
of vWF in plasma (as well as C-reactive protein) compared with UFH. Enoxaparin had
a more favorable effect on glycoprotein Ib/IX complexes than either dalteparin or
UFH. The incidence of the composite clinical efficacy end point was: 13% (enoxaparin),
19% (dalteparin), and 28% (UFH). vWF and its receptor glycoprotein Ib/IX play a key
role in acute coronary syndromes. vWF is linked to inflammation and, like glycoprotein
Ib/IX, is affected more favorably by the LWMHs than by UFH.